High temperature and high pressure apparatus



Nbv. 7, 1967 HIROSHI ISHIZUKA 3,350,743

HIGH TEMPERATURE AND HIGH PRESSURE APPARATUS Filed Oct. 29. 1965 5 sheets sheet 1 FIG I k V V 5 Q h r 4". 4H Q /I l8' H Nov. 7, 1967 HIROSHI ISHIZUKA 3,350,743

HIGH TEMPERATURE AND HIGH PRESSURE APPARATUS Filed Oct. 29, 1965 3 Sheets-Sheet 53 FIG. 2A

N v- 7, 6 HIROSHI ISHIZUKA 3,350,743

HIGH TEMPERATURE AND HIGH PRESSURE APPARATUS Filed Oct. 29, 1965 5 Sheets-Sheet 5 FIG. 3

I I l United States Patent Office 3,350,743 Patented Nov. 7, 1967 3,350,743 HIGH TEMPERATURE AND HIGH PRESSURE APPARATUS Hiroshi Ishizuka, 19-2 Ebara 6-chomc, Shinagawa-kn, Tokyo, Japan Filed Oct. 29, 1965, Ser. No. 505,644 Claims priority, application Japan, Nov. 4, 1964, 39/62,364; Feb. 18, 1965, 40/9,239; May 4, 1965, ill/26,087

3 Claims. (Cl. 18-16.5)

ABSTRACT OF THE DISCLOSURE Apparatus for the synthesizing of diamonds having a pair of opposed tapered pistons or punches each having a truncated or flat end surface, an annular die member having a substantially cylindrical Wall of a diameter larger than that of each piston truncated end surface, a hollow cylindrical body made of less compressibility coefficient material than the die material and having an outer diameter substantially the same or slightly smaller than the diameter of said flat end surface of each piston and positioned eoaxially within the die cylindrical wall, and gaskets placed respectively at the ends of said cylindrical body, the reactant being compressed and heated within a reaction chamber within the hollow body, the pressure and temperature directed to the reactant being higher than that on the die by the interposed damping effect of the hollow body thereby preserving the die.

This invention relates to a high temperature and high pressure apparatus and more particularly to such apparatus for synthesizing diamonds, durable to the pressure above 40,000 atmospheres and concurrently to the temperature above 1,200 C. for sustained time intervals, in which the temperature and pressure can be controlled at will.

This invention is based on the principle of the Bridgeman anvil and that of the Drickamer high pressure apparatus which has developed from said anvil. thus, the apparatus according to the present invention belongs to a category different from that of so-called belt device ineluding the apparatus of General Electric Company of USA. which has been disclosed in Japanese Patent No. 311,237 corresponding to US. Patent 2,941,248. In the General Electric Company apparatus an annular pressureresisting member or die, which is coaxially positioned between a pair of opposed tapered punches, has a convergent-divergent aperture therein so that movement of one of the punches develops hydrostatic pressure in the reac tion vessel with accompanying resolving of forces in the punches and the pressure resisting member. Namely, the combination of the punch and the die configuration resolves the force in the die so as to prevent fracture of the die material due to the high pressure exceeding the limit of mechanical strength of said die material.

In contradistinction to the GE. apparatus, the maximum pressure caused in or by the apparatus according to this invention is not applied directly to the die member because the cylindrical body, containing the raw material to be subjected to the reaction for synthesizing diamond and which body is positioned in the reaction chamber, will damp the pressure to be directed to the die. In the Bridgeman anvil type devices a fundamental fault is that the thickness of the reaction material is restricted. The present invention provides high temperature and high pressure apparatus capable of containing a relatively large amount of reactant, and, consequently, produces a relatively large amount of diamond in each operation because of features thereof to be disclosed hereinafter.

This invention will be better understood from the following explanation of the preferred embodiments taken in connection with the accompanying drawings, in which:

FIG. 1 is a diagrammatic view in section of the essential portion of the apparatus according to this invention,

FIG. 2A shows various configurations and positions of the gasket to be used for said apparatus,

FIG. 2B shows another configuration of the gasket, and

FIG. 3 is a diagram similar to FIG. 1 showing a modification of the present invention.

The piston may be truncated conical configuration as illustrated by 11 in FIG. 1 or of similar configuration. This is for the purpose of strengthening the piston by adding mass at the outer portion thereof. In the modification shown in FIG. 3, the piston has two differently tapered or curved surfaces. For the purpose of preventing the shoulder of the die member from being broken, and for making the height or axial length of the cylindrical body larger. The angle of the tapered surface is preferably 45 to 20 and more preferably 40 to 25 relative to the axial or a vertical line with the view of strengthening the piston by means of mass supporting. In the case where two diiferent angles of surfaces are formed, the second surface or the surface remote from the truncated flat end surface is tapered at an angle ranging 30 to 0 and more preferably 20 to 5 in relation to the vertical axis.

The material to be used for the piston is generally WC-Co alloy, but alloy steel may be used which has been subjected to quenching so that inner portion thereof may remain unhardened and the outer portion hardened. When a relatively lower pressure is employed in the apparatus, alloy steel sufliciently hardened up to the inside thereof may be used.

The annular die member has an inner cylindrical wall and connecting surfaces respectively tapered opposedly at an angle to said wall for the purpose as referred to above with respect to the piston. The wall is preferably vertical but there may be provided further intermediate tapered or curved surfaces respectively connecting each of said strengthening tapered surfaces with the vertical Wall defining a cylindrical chamber to snugly contain the hollow cylindrical body so that the shoulder may be minimized. Alternatively, the inner wall may be smoothly curved. The ratio of the diameter of the cylindrical Wall of the die member to that of the truncated flat end surface of the piston should be less than 0.8 for the reasons to be referred to hereinafter. Said ratio is more preferably such that the square of the former to that of the latter is less than 0.5 in case of the die member is to be made of WC-Co alloy. When it is of carbon steel or of alloy steel said ratio must be less than 0.4 and preferably is less than 0.3.

The height or axial length of the cylindrical wall is generally less than the dimension of the diameter thereof. If the length is made longer the pressure resistibility of the die member is lowered because of the decrease of the amount of pressure absorption or damping of the hollow cylindrical body.

The die member is preferably pre-stressed by a plurality of binding rings made of hardened steel so as to counteract the tensile stress to occur in the die member. The tapered surfaces of the die member are provided in order to strengthen it due to so-called mass support by making the outward portion thick, and to prevent the shoulder portion from being broken. The strengthening angle may be more decreased if the portion to be stressed is positioned further inwardly or if the force to be applied to the die member is lowered.

The hollow cylindrical body is located in the reaction chamber defined by the cylindrical wall of the die and serves to prevent the temperature and pressure in the reaction chamber from being directly applied to the cylindrical wall which may otherwise cause rupture of the die member. The cylindrical body may be made of alumina, magnesia, zirconia, thoria, beryllia, titania or other oxides which are rigid and of relatively lower compressibility coefficient and which are preferably sintered sufficiently so that the apparent specific gravity thereof comes, close to the true specific gravity. Other refractory products comprising some constituent in addition to said oxide also may be used for that purpose but in such case the pressure damping effect is lowered to some extent. It is due to the fact that the cylindrical body is supported by the gaskets at the opposed ends thereof, which seal the gaps between the pistons and die member, that the rupture of said cylindrical body due to expansion in the vertical direction may be prevented. The cylindrical body may thus be used under severe temperature and pressure conditions under which the body material per se cannot withstand. The status corresponding to the so-called quasiisotropic pressure realized in the known high pressure apparatus is established in said cylindrical body.

The pressure damping is computed by applied Lams formulae prescribing the approximate pressure decrement in the thick wall of cylinder. Now supposing that the inner pressure is represented by P the inner diameter of the die member by r, the inner diameter of the cylindrical body by 1' and the outer diameter of the die member by r then various stresses seem to be in inverse proportion to the square values of the ratio of the diameters as seen from the following formulae;

Maximum shearing stress (Circumferential stress- T12 Radial stress) 1;

The pressure resistibility of the cylindrical body is varied depending on the material used for constructing said body. The maximum pressure resistibility can be attained when alumina is used, while in case where thoria, zirconia, magnesia or the like is used the result is more or less inferior.

The inner diameter of the hollow cylindrical body may be that of the diameter of the truncated end surface of the piston or slightly smaller than the diameter of the piston free end, depending on the axial length of the reactant to be filled in said cylindrical body. The axial length or the height of the cylindrical body should be some smaller than that of the inner cylindrical wall of the die member since the gaskets must be placed at the Opposite ends of said cylindrical body.

On each end of the cylindrical body and in the adjacent gap between a piston and the died member is placed a substantially annular gasket, which may be made of the refractory comprising agalmatolite stone-like material having a relatively higher porosity which is preferably sintered slightly. The refractory is preferably wrapped or sandwiched with well-tempered copper or iron foil. Other similar stony refractory materials such as natural agalmatolite, steatite and the like, various fibers, as well as plastics such as Teflon, polyethylene and the like may be used for this purpose. As referred to hereinafter and as illustrated in FIGS. 2A and 2B the gasket is placed at the area where there is an absence of temperature to effect such material.

The configuration of the gasket may be varied in cross section as seen in FIGS. 2A and 2B. There is recognized no remarkable difference in effect and function thereof except in the treatment for mounting the gaskets.

The gasket serves to seal the pressure produced in the reaction chamber and insulate the die member from electric current flowing from one of the pistons to the other through the reactant contained in the cylindrical body in order to produce the high temperature necessary for the reaction. Thus the gasket used in the present invention is utterly different in configuration, location, and function from the usual gasket used in the known high temperature, high pressure apparatuses.

In FIG. 1, reference numeral 11 designates a tapered piston made of an WC-Co alloy. The strengthening wall of said piston is tapered by an angle al, 30. The piston is surrounded by a binding ring 12 made of hardened steel which serves to strengthen the piston by pre-stressing. A plurality of such rings may be mounted by well known methods in order to avoid rupture of the piston due to high pressure and high temperature. A piston 11 having a strengthening ring 12 is provided in confronting relation to piston 11.

A substantially annular die member 13 is oriented in such a way that the inner cylindrical wall thereof is coaxially positioned between said two opposed pistons 11 and 11. As seen in FIG. 1, the die member is defined in section by line segments cb, 12-12 and bc'. The segment b-b constitutes the inner wall of the die member which is made flat and substantially vertical. The segments b-c and bc' constitute strengthening walls and are tapered at an angle :12 of 30. In this embodiment the die member is made of WC-Co alloy with the inner diameter thereof being 22 mm. The die member 13 is also surrounded by a plurality of binding rings, one of which is illustrated at 14 in FIG. 1, and is made of hardened steel which serves to pre-stress the die member to prevent rupture thereof. A ring (not shown) Was made of mild steel is provided to overlie rang 14 in order to prevent danger from flying bits of metal should explosion of the apparatus or the die member occur.

Numeral 15 designates a hollow cylindrical body which is made of magnesia sintered at a temperature above 2,000 C. such that the apparent specific gravity comes close to the true one. The inner diameter thereof is 16 mm., and the outer surface is abraded so that it may be snugly inserted in the aperature of the die member, the diameter of which is 22 mm. as referred to above. The opposite ends of the cylindrical body are also subjected to grinding so that the axial length thereof comes to 10 to 12 mm. and so that the end surfaces thereof be smooth. This cylindrical body serves, as stated above, to dampen the high pressure and temperature caused by the movement of the pistons toward one another so that the die member may not be subjected directly to such severe conditions. This feature and coaction constitutes an essential element of this invention. It can serve also to thermally and electrically insulate the die member since it is made of the hereinbefore mentioned oxide or refractory product.

Although the die member is insulated by means of said cylindrical body from high temperature in the reaction chamber and from electrical current, it is preferable to provide a further thermal and electrical insulator. In the embodiment as illustrated in FIG. 1, there is provided a cylindrical member 16 made of sintered agalmatolite which forms a reactant vessel together with two discs 19, 19 respectively made of black lead or graphite. Between the receptacle assembly, consisting of the cylindrical member 16 and discs 19, 19', and the end surfaces of the pistons 11 and 11 pairs of discs 17, 20 and 17', 20' are inserted respectively. Each disc 17, 17' is made of sintered agalmatolite or the like, around the periphery of which a ring 18 made of steel is provided which forms an electric current path together with the disc 20, 20, also made of steel, through graphite disc 19, 19'. In the vessel a specimen or reactant 21 is contained.

Numerals 22 and 22' are designate gaskets which are made of agalmatolite system refractory which has been slightly sintered at a temperature such that the porosity comes to 20 to 30%, which may be sandwiched with tempered copper or iron foil, as having been referred to. Various configurations and locations of the gasket relative to the pistons, die member and cylindrical body are illustrated at P, Q, R and S in FIG. 2A. The gasket P is positioned in such a way that it surrounds the piston inside of a horizontal plane intersecting the tapered surface which would contact with the shoulder or edge b (FIG. 1) of the die member if either of the two pistons should have been moved close together into the aperture of the die. It will be noted that the gasket Q lies wholly inside of a horizontal plane intersecting the tapered surface of the piston and to which is drawn a perpendicular from the shoulder or edge "12 (FIG. 1) of the die member, and the gasket R lies wholly in the area of the vertical wall of the die member. The gasket S, which is used in the embodiment of FIG. 1, is positioned similarly to the gasket P, but which is provided with a protruding portion helpful for mounting the gasket in the apparatus. The simplest gasket may take the configuration and position as shown by T in FIG. 2B. In this case the gasket is made of fibrous material. The gaskets of this invention, particularly those identified as Q, R in FIG. 2A and T in FIG. 2B, are utterly distinct from those used in the usual apparatuses since their function to seal the pressure within the reaction chamber is not due to compression, but instead to the deformation.

The apparatus is mounted in an hydraulic press so as to move the punches respectively into the die aperture to produce high pressure between the truncated end surfaces thereof. Since this area is surrounded by the die member 13 and gaps between the die member and pistons or punches 11, 11' are sealed with gaskets 22, 22', the pressure in the reaction chamber containing reactant 21 may be raised up to 50,000 atmosphers. As stated this high pressure will not be transmitted directly to the wall of the die member owing to the pressure of the interposed cylindrical body 15. From an electric source, not shown, electrical current is applied to the punch 11 which flows through the ring 18, the disc 20, the disk 19, the reactant 21 and through the corresponding members on the other side in reverse direction to the other punch 11', or vice versa, so as to cause a temperature of 1,200- 1,400 C. The reactant, which is prepared by admixing particles of nickel and chromium carbide and adding thereto graphite, is thus synthesized to form diamond. This apparatus has endured several thousands of operations.

A modification of the present invention is illustrated in FIG. 3, wherein the pistons are designated by 111 and 111 which are also made of WC-Co alloy. The diameter of the truncated end surface of each piston is 26 mm. The strengthening wall is tapered at an angle 35 relative to the vertical axis and this inclination is changed at a point where the piston has a diameter of 45 mm. to The root of the piston has 70 mm. of diameter. By 112 is represented one of the strengthening rings as 12 and 12' in FIG. 1. Similarly a die member 113 is strengthened by a binding ring 114. The former is made to carbon steel or alloy steel which has been subjected to quenching to be hardened at least to be Re 50. It is preferable to use the material of above Re 60 but it is not absolutely necessary owing to the pressure damping effect of the cylindrical body. The inner diameter of the die member 113 is 50 mm. The axial length of inner wall thereof, which may range from 40 mm. to 50 mm. in relation to the dimensions and conditions as referred to above, is 45 mm. in this embodiment. This inner wall may be slightly deformed due to operation but can be reformed by abrading or cutting. A hollow cylindrical body 115 has 30 mm. inner diameter and the outer surface is ground by means of diamond abrasive so as to be snuggly fitted in the aperture of the die member which is defined by said inner wall. The axial length thereof may range from 20 mm. to 30 mm. The cylindrical body is formed by means of a hot press at a temperature above 2,000 C. from alumina to which is preferably added about 1% of iron oxide in order to lower the sintering temperature. The formed article is almost nonporous and has an apparent specific gravity quite close to the true specific gravity. In this case gasket 122 and 122' are formed and positioned as Q or R in FIG. 2A and thus the strokes of the pistons extend within the gaskets. It should be noted that the truncated end surfaces of the pistons would be contacted with each other if the gaskets and other members in the reaction chamber did not exist, but the die member would not contact the pistons as in the apparatus of FIG. 1. After placing the reactant, comprising particles of cobalt and pulverized graphite, in the vessel and subjecting the reactant to complete reduction by means of carbon monooxide, the punches 111 and 111 are moved into the die member aperture to bring the reactant under 50,000 atmospheres of pressure. Concurrently electric current is applied so as to raise the reactant temperature up to 1,300 to 1,500 C. In this manner, 2 grams or more of diamond have been synthesized in each operation, and the apparatus has been repeatedly used over an extended period of time.

The descriptions given hereinabove in connection with the drawings have been made merely in order to explain the invention and it is to be noted that various modifications in configuration, position, material and the like can be readily made by those skilled in the art without departing from the spirit and scope of this invention. For instance, the inner wall of the die member is flat and vertical in section in the embodiments shown but may be curved slightly if desired. Correspondingly, the configuration and construction of the hollow cylindrical body may be variously modified. It is, however, an essential feature of this invention to provide a rigid and hollow cylindrical body with a position about the reaction chamber gaskets on the opposite: ends thereof to damp high pressure and high temperature in the reactant to or below the elastic limit of the material constituting said die member as well as to select the dimensions of the elements so as to cause such pressure damping or decrement. It should be noted that even if the apparatus is constructed of the elements or members as referred to above, the desired purpose, namely the commercially desirable pressure resistibility of the die member and lifespan of the apparatus can not be attained without proper selection of the interrelated dimensions of the elements as defined.

Thus, the scope of the invention is limited to an apparatus for commercially synthesizing diamond comprising the pistons, the die member, the hollow cylindrical body and the gaskets of which dimensions and arrangement make the apparatus endure severe conditions for synthesizing diamond owing to the pressure and temperature damping effect of said cylindrical body.

What I claim is:

1. A high temperature high pressure apparatus comprising a pair of opposed tapered pistons respectively having a truncated flat end surface, an annular die member having a straight cylindrical inner wall, said Wall defining an aperture into which said pistons converge, a rigid hollow cylindrical body made of material having a relatively lower compressibility coefiicient than that of the material of the die member, said body being coaxially placed in said aperture, a reaction chamber formed by the piston ends and the inner Wall of the body, and gaskets placed respectively upon the ends of said cylindrical body and, sealing the gaps between said pistons and die inner cylindrical wall, the temperature and pressure caused in the reaction chamber being damped by said cylindrical body thereby lowering the pressure and temperature transmitted to said die member, said gaskets deforming upon lengthening of the body whereby the body walls are prevented from rupturing at a pressure higher than that induced by the material of the body per 2. The apparatus as set forth in claim 1, wherein said rigid hollow cylindrical body is made of a material selected from a group consisting of alumina, magnesia, zirconia, thoria and beryllia, and the gaskets are made of a material comprising sintered porous refractories taken from the group consisting of agalmatolite and steatite.

3. The apparatus as set forth in claim 2, wherein the material of the body is sufficiently sintered so that the apparent specific gravity comes close to the true one.

References Cited UNITED STATES PATENTS 2,941,241 6/1960 Strong. 2,941,252 6/1960 Bovenkerk. 2,996,763 8/1961 Wentorf. 3,030,662 4/1962 Strong. 3,082,477 3/1963 Custers et a1. 3,137,896 6/1964 Daniels.

WILLIAM J. STEPHENSON, Primary Examiner. 

1. A HIGH TEMPERATURE HIGH PRESSURE APARATUS COMPRISING A PAIR OF OPPOSED TAPERED PISTONS RESPECTIVELY HAVING A TRUNCATED FLAT END SURFACE, AN ANNULAR DIE MEM- 